scholarly journals Dimerization through the helix-loop-helix motif enhances phosphorylation of the transcription activation domains of myogenin.

1994 ◽  
Vol 14 (9) ◽  
pp. 6232-6243 ◽  
Author(s):  
J Zhou ◽  
E N Olson
Keyword(s):  
Transcriptional Activity ◽  
Transcription Activation ◽  
Bhlh Protein ◽  
Specific Gene ◽  
Phosphorylation Sites ◽  
Gene Products ◽  
Activation Domains ◽  
Helix Loop Helix ◽  
Carboxyl Terminal ◽  
Bhlh Proteins

The muscle-specific basic helix-loop-helix (bHLH) protein myogenin activates muscle transcription by binding to target sequences in muscle-specific promoters and enhancers as a heterodimer with ubiquitous bHLH proteins, such as the E2A gene products E12 and E47. We show that dimerization with E2A products potentiates phosphorylation of myogenin at sites within its amino- and carboxyl-terminal transcription activation domains. Phosphorylation of myogenin at these sites was mediated by the bHLH region of E2A products and was dependent on dimerization but not on DNA binding. Mutations of the dimerization-dependent phosphorylation sites resulted in enhanced transcriptional activity of myogenin, suggesting that their phosphorylation diminishes myogenin's transcriptional activity. The ability of E2A products to potentiate myogenin phosphorylation suggests that dimerization induces a conformational change in myogenin that unmasks otherwise cryptic phosphorylation sites or that E2A proteins recruit a kinase for which myogenin is a substrate. That phosphorylation of these dimerization-dependent sites diminished myogenin's transcriptional activity suggests that these sites are targets for a kinase that interferes with muscle-specific gene expression.

Dimerization through the helix-loop-helix motif enhances phosphorylation of the transcription activation domains of myogenin

1994 ◽  
Vol 14 (9) ◽  
pp. 6232-6243
Author(s):  
J Zhou ◽  
E N Olson
Keyword(s):  
Transcriptional Activity ◽  
Transcription Activation ◽  
Bhlh Protein ◽  
Specific Gene ◽  
Phosphorylation Sites ◽  
Gene Products ◽  
Activation Domains ◽  
Helix Loop Helix ◽  
Carboxyl Terminal ◽  
Bhlh Proteins

The muscle-specific basic helix-loop-helix (bHLH) protein myogenin activates muscle transcription by binding to target sequences in muscle-specific promoters and enhancers as a heterodimer with ubiquitous bHLH proteins, such as the E2A gene products E12 and E47. We show that dimerization with E2A products potentiates phosphorylation of myogenin at sites within its amino- and carboxyl-terminal transcription activation domains. Phosphorylation of myogenin at these sites was mediated by the bHLH region of E2A products and was dependent on dimerization but not on DNA binding. Mutations of the dimerization-dependent phosphorylation sites resulted in enhanced transcriptional activity of myogenin, suggesting that their phosphorylation diminishes myogenin's transcriptional activity. The ability of E2A products to potentiate myogenin phosphorylation suggests that dimerization induces a conformational change in myogenin that unmasks otherwise cryptic phosphorylation sites or that E2A proteins recruit a kinase for which myogenin is a substrate. That phosphorylation of these dimerization-dependent sites diminished myogenin's transcriptional activity suggests that these sites are targets for a kinase that interferes with muscle-specific gene expression.

scholarly journals An activation domain of the helix-loop-helix transcription factor E2A shows cell type preference in vivo in microinjected zebra fish embryos.

1996 ◽  
Vol 16 (4) ◽  
pp. 1714-1721 ◽  
Author(s):  
F Argenton ◽  
Y Arava ◽  
A Aronheim ◽  
M D Walker
Keyword(s):  
Gene Expression ◽  
Nervous System ◽  
Transcription Factor ◽  
Transcription Activation ◽  
Cell Types ◽  
Zebra Fish ◽  
Reporter Plasmid ◽  
Activation Domains ◽  
Helix Loop Helix

The E2A protein is a mammalian transcription factor of the helix-loop-helix family which is implicated in cell-specific gene expression in several cell lineages. Mouse E2A contains two independent transcription activation domains, ADI and ADII; whereas ADI functions effectively in a variety of cultured cell lines, ADII shows preferential activity in pancreatic beta cells. To analyze this preferential activity in an in vivo setting, we adapted a system involving transient gene expression in microinjected zebra fish embryos. Fertilized one- to four-cell embryos were coinjected with an expression plasmid and a reporter plasmid. The expression plasmids used encode the yeast Gal4 DNA-binding domain (DBD) alone, or Gal4 DBD fused to ADI, ADII, or VP16. The reporter plasmid includes the luciferase gene linked to a promoter containing repeats of UASg, the Gal4-binding site. Embryo extracts prepared 24 h after injection showed significant luciferase activity in response to each of the three activation domains. To determine the cell types in which the activation domains were functioning, a reporter plasmid encoding beta-galactosidase and then in situ staining of whole embryos were used. Expression of ADI led to activation in all major groups of cell types of the embryo (skin, sclerotome, myotome, notochord, and nervous system). On the other hand, ADII led to negligible expression in the sclerotome, notochord, and nervous system and much more frequent expression in the myotome. Parallel experiments conducted with transfected mammalian cells have confirmed that ADII shows significant activity in myoblast cells but little or no activity in neuronal precursor cells, consistent with our observations in zebra fish. This transient-expression approach permits rapid in vivo analysis of the properties of transcription activation domains: the data show that ADII functions preferentially in cells of muscle lineage, consistent with the notion that certain activation domains contribute to selective gene activation in vivo.

scholarly journals Displacement of an E-box-binding repressor by basic helix-loop-helix proteins: implications for B-cell specificity of the immunoglobulin heavy-chain enhancer.

1994 ◽  
Vol 14 (9) ◽  
pp. 6153-6163 ◽  
Author(s):  
T Genetta ◽  
D Ruezinsky ◽  
T Kadesch
Keyword(s):  
B Cells ◽  
B Cell ◽  
Heavy Chain ◽  
Zinc Finger Protein ◽  
Immunoglobulin Heavy Chain ◽  
Bhlh Protein ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
E Box ◽  
Bhlh Proteins

The activity of the immunoglobulin heavy-chain (IgH) enhancer is restricted to B cells, although it binds both B-cell-restricted and ubiquitous transcription factors. Activation of the enhancer in non-B cells upon overexpression of the basic helix-loop-helix (bHLH) protein E2A appears to be mediated not only by the binding of E2A to its cognate E box but also by the resulting displacement of a repressor from that same site. We have identified a "two-handed" zinc finger protein, denoted ZEB, the DNA-binding specificity of which mimics that of the cellular repressor. By employing a derivative E box that binds ZEB but not E2A, we have shown that the repressor is active in B cells and the IgH enhancer is silenced in the absence of binding competition by bHLH proteins. Hence, we propose that a necessary prerequisite of enhancer activity is the B-cell-specific displacement of a ZEB-like repressor by bHLH proteins.

scholarly journals SclR, a Basic Helix-Loop-Helix Transcription Factor, Regulates Hyphal Morphology and Promotes Sclerotial Formation in Aspergillus oryzae

2011 ◽  
Vol 10 (7) ◽  
pp. 945-955 ◽  
Author(s):  
Feng Jie Jin ◽  
Tadashi Takahashi ◽  
Ken-ichiro Matsushima ◽  
Seiichi Hara ◽  
Yasutomo Shinohara ◽  
...  
Keyword(s):  
Aspergillus Oryzae ◽  
Cell Function ◽  
Egfp Expression ◽  
Bhlh Protein ◽  
Protein Fusion ◽  
Content Type ◽  
Helix Loop Helix ◽  
Hyphal Morphology ◽  
Bhlh Proteins ◽  
Overexpressing Strain

ABSTRACT Most known basic-region helix-loop-helix (bHLH) proteins belong to a superfamily of transcription factors often involved in the control of growth and differentiation. Therefore, inappropriate expression of genes encoding bHLH proteins is frequently associated with developmental dysfunction. In our previously reported study, a novel bHLH protein-encoding gene (AO090011000215) of Aspergillus oryzae was identified. The gene-disrupted strain was found to produce dense conidia, but sparse sclerotia, relative to the parent strain. Here, to further analyze its function, we generated an overexpressing strain using the A. oryzae amyB gene promoter. Genetic overexpression led to a large number of initial hyphal aggregations and then the formation of mature sclerotia; it was therefore designated sclR ( scl erotium r egulator). At the same time, the sclR -overexpressing strain also displayed both delayed and decreased conidiation. Scanning electron microscopy indicated that the aerial hyphae of the sclR -overexpressing strain were extremely branched and intertwined with each other. In the generation of the SclR-enhanced green fluorescent protein (EGFP) expression strain, the SclR-EGFP protein fusion was conditionally detected in the nuclei. In addition, the loss of sclR function led to rapid protein degradation and cell lysis in dextrin-polypeptone-yeast extract liquid medium. Taken together, these observations indicate that SclR plays an important role in hyphal morphology, asexual conidiospore formation, and the promotion of sclerotial production, even retaining normal cell function, at least in submerged liquid culture.

scholarly journals Extramacrochaete promotes branch and bouton number via the sequestration of Daughterless in the cytoplasm of neurons

2019 ◽  
Author(s):  
Edward A. Waddell ◽  
Jennifer M. Viveiros ◽  
Erin L. Robinson ◽  
Michal A. Sharoni ◽  
Nina K. Latcheva ◽  
...  
Keyword(s):  
Class I ◽  
Bhlh Protein ◽  
Tissue Specific ◽  
Consensus Sequences ◽  
Helix Loop Helix ◽  
Molecular Logic ◽  
E Box ◽  
Mature Neurons ◽  
Type V ◽  
Bhlh Proteins

AbstractThe class I basic Helix Loop Helix (bHLH) proteins are highly conserved transcription factors that are ubiquitously expressed. A wealth of literature on class I bHLH proteins have shown that these proteins must homodimerize or heterodimerize with tissue specific HLH proteins in order to bind DNA at E box (CANNTG) consensus sequences to control tissue specific transcription. Due to its ubiquitous expression, class I bHLH proteins are also extensively regulated post-translationally, mostly through dimerization. Previously, we reported that in addition to its role in promoting neurogenesis, the class I bHLH protein Daughterless also functions in mature neurons to restrict axon branching and synapse number. Here, we show that part of the molecular logic that specifies how Daughterless functions in neurogenesis is also conserved in neurons. We show that the type V HLH protein Extramacrochaete binds to and represses Daughterless function by sequestering Daughterless to the cytoplasm. This work provides initial insights into the mechanisms underlying the function of Daughterless and Extramacrochatae in neurons while providing a novel understanding of how Extramacrochaetae functions to restricts Daughterless activity within the cell.

scholarly journals Multiple Basic Helix-Loop-Helix Proteins Regulate Expression of the ENO1 Gene of Saccharomyces cerevisiae

2007 ◽  
Vol 6 (5) ◽  
pp. 786-796 ◽  
Author(s):  
Meng Chen ◽  
John M. Lopes
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dominant Negative ◽  
Bhlh Protein ◽  
Dominant Negative Mutant ◽  
Eukaryotic Transcription ◽  
Control Of Gene Expression ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
E Boxes ◽  
Bhlh Proteins

ABSTRACT The basic helix-loop-helix (bHLH) eukaryotic transcription factors have the ability to form multiple dimer combinations. This property, together with limited DNA-binding specificity for the E box (CANNTG), makes them ideally suited for combinatorial control of gene expression. We tested the ability of all nine Saccharomyces cerevisiae bHLH proteins to regulate the enolase-encoding gene ENO1. ENO1 was known to be activated by the bHLH protein Sgc1p. Here we show that expression of an ENO1-lacZ reporter was also regulated by the other eight bHLH proteins, namely, Ino2p, Ino4p, Cbf1p, Rtg1p, Rtg3p, Pho4p, Hms1p, and Ygr290wp. ENO1-lacZ expression was also repressed by growth in inositol-choline-containing medium. Epistatic analysis and chromatin immunoprecipitation experiments showed that regulation by Sgc1p, Ino2p, Ino4p, and Cbf1p and repression by inositol-choline required three distal E boxes, E1, E2, and E3. The pattern of bHLH binding to the three E boxes and experiments with two dominant-negative mutant alleles of INO4 and INO2 support the model that bHLH dimer selection affects ENO1-lacZ expression. These results support the general model that bHLH proteins can coordinate different biological pathways via multiple mechanisms.

scholarly journals Akt Regulates Basic Helix-Loop-Helix Transcription Factor-Coactivator Complex Formation and Activity during Neuronal Differentiation

2003 ◽  
Vol 23 (13) ◽  
pp. 4417-4427 ◽  
Author(s):  
Anne B. Vojtek ◽  
Jennifer Taylor ◽  
Stacy L. DeRuiter ◽  
Jenn-Yah Yu ◽  
Claudia Figueroa ◽  
...  
Keyword(s):  
Growth Factors ◽  
Complex Formation ◽  
Neuronal Differentiation ◽  
Protein Function ◽  
Bhlh Protein ◽  
Akt Inhibitor ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Peptide Growth Factors ◽  
Bhlh Proteins

ABSTRACT Neural basic helix-loop-helix (bHLH) transcription factors regulate neurogenesis in vertebrates. Signaling by peptide growth factors also plays critical roles in regulating neuronal differentiation and survival. Many peptide growth factors activate phosphatidylinositol 3-kinase (PI3K) and subsequently the Akt kinases, raising the possibility that Akt may impact bHLH protein function during neurogenesis. Here we demonstrate that reducing expression of endogenous Akt1 and Akt2 by RNA interference (RNAi) reduces neuron generation in P19 cells transfected with a neural bHLH expression vector. The reduction in neuron generation from decreased Akt expression is not solely due to decreased cell survival, since addition of the caspase inhibitor z-VAD-FMK rescues cell death associated with loss of Akt function but does not restore neuron formation. This result indicates that Akt1 and Akt2 have additional functions during neuronal differentiation that are separable from neuronal survival. We show that activated Akt1 enhances complex formation between bHLH proteins and the transcriptional coactivator p300. Activated Akt1 also significantly augments the transcriptional activity of the bHLH protein neurogenin 3 in complex with the coactivators p300 or CBP. In addition, inhibition of endogenous Akt activity by the PI3K/Akt inhibitor LY294002 abolishes transcriptional cooperativity between the bHLH proteins and p300. We propose that Akt regulates the assembly and activity of bHLH-coactivator complexes to promote neuronal differentiation.

scholarly journals Molecular mechanisms of myogenic coactivation by p300: direct interaction with the activation domain of MyoD and with the MADS box of MEF2C.

1997 ◽  
Vol 17 (2) ◽  
pp. 1010-1026 ◽  
Author(s):  
V Sartorelli ◽  
J Huang ◽  
Y Hamamori ◽  
L Kedes
Keyword(s):  
Molecular Mechanisms ◽  
Direct Interaction ◽  
Dominant Negative ◽  
Physical Interaction ◽  
Activation Domain ◽  
Activation Domains ◽  
Amino Terminal ◽  
Helix Loop Helix ◽  
Dominant Negative Mutation ◽  
Bhlh Proteins

By searching for molecules that assist MyoD in converting fibroblasts to muscle cells, we have found that p300 and CBP, two related molecules that act as transcriptional adapters, coactivate the myogenic basic-helix-loop-helix (bHLH) proteins. Coactivation by p300 involves novel physical interactions between p300 and the amino-terminal activation domain of MyoD. In particular, disruption of the FYD domain, a group of three amino acids conserved in the activation domains of other myogenic bHLH proteins, drastically diminishes the transactivation potential of MyoD and abolishes both p300-mediated coactivation and the physical interaction between MyoD and p300. Two domains of p300, at its amino and carboxy terminals, independently function to both mediate coactivation and physically interact with MyoD. A truncated segment of p300, unable to bind MyoD, acts as a dominant negative mutation and abrogates both myogenic conversion and transactivation by MyoD, suggesting that endogenous p300 is a required coactivator for MyoD function. The p300 dominant negative peptide forms multimers with intact p300. p300 and CBP serve as coactivators of another class of transcriptional activators critical for myogenesis, myocyte enhancer factor 2 (MEF2). In fact, transactivation mediated by the MEF2C protein is potentiated by the two coactivators, and this phenomenon is associated with the ability of p300 to interact with the MADS domain of MEF2C. Our results suggest that p300 and CBP may positively influence myogenesis by reinforcing the transcriptional autoregulatory loop established between the myogenic bHLH and the MEF2 factors.

scholarly journals Decoding Hematopoietic Specificity in the Helix-Loop-Helix Domain of the Transcription Factor SCL/Tal-1

2004 ◽  
Vol 24 (17) ◽  
pp. 7491-7502 ◽  
Author(s):  
Thorsten M. Schlaeger ◽  
Anna Schuh ◽  
Simon Flitter ◽  
Andreas Fisher ◽  
Hanna Mikkola ◽  
...  
Keyword(s):  
Cell Fate ◽  
Control Cell ◽  
Embryonic Stem ◽  
Class Ii ◽  
Bhlh Protein ◽  
Hematopoietic Development ◽  
Helix Loop Helix ◽  
Critical Residues ◽  
Bhlh Proteins ◽  
Insight Into

ABSTRACT The helix-loop-helix (HLH) domain is employed by many transcription factors that control cell fate choice in multiple developmental settings. Previously, we demonstrated that the HLH domain of the class II basic HLH (bHLH) protein SCL/Tal-1 is critical for hematopoietic specification. We have now identified residues in this domain that are essential for restoring hematopoietic development to SCL−/− embryonic stem cells and sufficient to convert a muscle-specific HLH domain to one able to rescue hematopoiesis. Most of these critical residues are distributed in the loop of SCL, with one in helix 2. This is in contrast to the case for MyoD, the prototype of class II bHLH proteins, where the loop seems to serve mainly as a linker between the two helices. Among the identified residues, some promote heterodimerization with the bHLH partners of SCL (E12/E47), while others, unimportant for this property, are still crucial for the biological function of SCL. Importantly, the residue in helix 2 specifically promotes interaction with a known partner of SCL, the LIM-only protein LMO2, a finding that strengthens genetic evidence that these proteins interact. Our data highlight the functional complexity of bHLH proteins, provide mechanistic insight into SCL function, and strongly support the existence of an active SCL/LMO2-containing multiprotein complex in early hematopoietic cells.

Homologous tyrosine phosphorylation sites in transformation-specific gene products of distinct avian sarcoma viruses

Nature ◽  
1981 ◽  
Vol 291 (5817) ◽  
pp. 675-677 ◽  
Author(s):  
James C. Neil ◽  
Jacques Ghysdael ◽  
Peter K. Vogt ◽  
John E. Smart
Keyword(s):  
Tyrosine Phosphorylation ◽  
Specific Gene ◽  
Phosphorylation Sites ◽  
Gene Products ◽  
Avian Sarcoma
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